i say the bowflex probably will work pretty good, in fact, its been around 15 years and i know people who like it.
but will it work as free weights?
probably not, for one, you won't be able to work the stabilizer muscles very much (or at all?) with the bowflex, and the bowflex does not directly duplicate some very important compound movements which are good releasers of growth hormone (bench, squats).
i say, anything is good as far as fitness and getting in shape goes, even a stairmaster will make you a healthier person, but if you are looking to get big and strong, and do it fairly fast, stick with free weights and basic compound movements (not forgetting diet). plus with the money to spend on a bowflex, you could buy a whole bunch of free weights / bench, etc.
like i say, im sure bowflex is good and everything, but...hit the gym